Hepatocyte RIPK1 scaffolding function protects against alcohol-induced liver injury by restraining ER stress-driven apoptosis and inflammation

Abstract

Alcoholic liver disease (ALD) is a global health burden with limited therapeutic options. The pathogenesis of ALD involves hepatocyte death and inflammation, but the key regulatory mechanisms remain incompletely defined. Receptor-interacting protein kinase 1 (RIPK1) is a critical signaling molecule with distinct kinase-dependent and kinase-independent, scaffold-dependent functions. While RIPK1 kinase activity has been implicated in various pathologies, the role of its scaffolding function in the liver, particularly in ALD, is unknown. Here, using hepatocyte-specific RIPK1 knockout ( Ripk1 -hepKO) mice, we demonstrate that loss of RIPK1 markedly aggravates ethanol-induced liver injury. In both chronic and acute-binge ethanol feeding models, Ripk1 -hepKO mice exhibited significantly elevated serum transaminases, enhanced hepatocyte apoptosis, and amplified hepatic inflammation with increased macrophage infiltration, without a change in steatosis. Transcriptomic analysis revealed enrichment of inflammatory pathways in Ripk1 -hepKO livers. Mechanistically, we identified endoplasmic reticulum (ER) stress as a critical contributor to this phenotype. RIPK1 deficiency was associated with attenuated NF-κB/p65 signaling, preferential amplification of eIF2α-ATF4-CHOP-associated stress responses, and enhanced CHOP accumulation, while pharmacological modulation of ER stress-associated pathways using 4-phenylbutyrate (4-PBA) or ISRIB ameliorated hepatocyte apoptosis, liver injury, and inflammation in ethanol-fed Ripk1 -hepKO mice. Translating these findings to human disease, liver specimens from ALD patients showed elevated hepatocyte apoptosis, CD68 + macrophage infiltration, and induction of ER stress markers. Our study unveils a previously unrecognized protective role for the scaffold function of hepatocyte RIPK1 in ALD, positioning RIPK1 scaffolding and ER stress-associated signaling as promising therapeutic targets for ALD.